Possibly the first water mine in
the world with a target-fired trigger (as opposed to earlier ones
which had simple, slow-burning fuzes) was invented by David
Bushnell, the man who is most famous for inventing a one-man
submersible, the Turtle. Like the Turtle, these sea mines were
unsuccessful when they were used against the British fleet in
Philadelphia during January 1778, although the resulting "Battle of
the Kegs" did cause a few casualties and inspired a well-known
Revolutionary War poem.

Bushnell's mine was a simple
watertight wooden keg, loaded with gunpowder, which hung from a
float. At that time, it was called a torpedo. Late in1777, under
orders from General George Washington, a number of these “torpedoes”
were set adrift by Bushnell in an attempt to destroy a fleet of
British warships anchored in the Delaware River near the city of
Philadelphia. That early attempt failed to achieve its goal, but the
naval mine has since gained a well‑deserved reputation as one of the
Navy's least costly, yet most effective offensive and defensive
weapons.

For most of the 19th century the
US Army was responsible for the development and use of mines, as
mines were considered to be defensive weapons that were useful for
protecting harbors and coastal waters. The Confederate Navy used
mines, or torpedoes, as they were then called, quite extensively
during the American Civil War, and sank approximately 27 Federal
vessels and damaged many more. By comparison, only nine Federal
vessels were sunk by gunfire. Many different kinds of mines were
used by the Confederates, with one of the most effective being the
frame torpedo, which was a large nose-fuzed artillery shell that was
mounted on a wooden frame and located where a ship might strike it.

Not until late in the 19th
century did the Navy start to take any interest in these weapons,
but none were used during the Spanish-American War of 1898 and it
was not until the Russo-Japanese War of 1905 that this interest
became serious. During that war, both Imperial Russia and Japan had
some success with their naval mines, which prompted the US Navy to
ask Congress for funds for a mine depot ship. The old cruiser USS
San Francisco (C-5) was converted in 1912 and she became the first
mine warfare ship in the US Navy.
The first mines procured by the Navy were originally called "Naval
Defense Mines" and were either purchased from European powers or
were copies of European designs. Progress on mines was considered
satisfactory prior to the start of World War I, but with the US
entry into the war it was discovered that British mines of the same
general types had proved unreliable. Bureau of Ordnance reports of
1917 declared that the status of mining in the USN with these Naval
Defense Mines was "very unsatisfactory" and recommended development
of new types, which led to the Mark 5 contact mine and the Mark 6
antenna mine.

These Naval Defense Mines were
all declared obsolete in 1930 and removed from inventory. None of
these designs were very successful, so perhaps it is surprising that
it took so long to take them out of service.

Triggering and Fuzes

The first USA designed mine, the
Mark 5, was of the "Horned" type. Horns were made of soft metal such
as lead and held a glass ampoule containing battery acid, usually
potassium-bichromate. The lower end of the horn contained an
electric battery minus the electrolyte. Contact with the horn broke
open the acid container, energizing the battery which then heated a
platinum wire in a mercury fulminate detonator, thus exploding the
mine. By definition, this was a weapon with limited range and fields
needed to be densely packed in order for it to be effective against
shipping. However, such close-laid fields ran the risk of one mine
setting off adjacent mines as fraternal kills.

This history of naval mines
is provided exclusively from unclassified sources, including:US Naval Weapons and Guide to World Naval
Weapons Systems, 1991/92, both by Norman Friedman and
are used by permission of the The U.S. Naval Institute

Other data has been provided from:

Naval Weapons of World War Two by John
Campbell America's Use of Sea Mines by Robert C.
Duncan, Ph.D. US Warships of World War II by Paul
Silverstone